The present invention relates generally to application devices, systems and methods for use with medical devices and, particularly, to application or attachment devices, systems and methods for use in the medical field to releasably attach a medical device such as a sensor to a patient (either a human patient or a so called lower animal patient).
Adhesive sheets or adhesive materials such as adhesive tapes are widely used in the medical field. For example, adhesive tapes are used to maintain certain medical devices (for example, catheters, sensors etc.) in close proximity to the body of a patient.
One type of sensor that can be adhered to patient is an extravasation sensor. Extravasation or infiltration is the accidental infusion or leakage of an injection fluid such as a contrast medium or a therapeutic agent into tissue surrounding a blood vessel rather than into the blood vessel itself. Extravasation can be caused, for example, by rupture or dissection of fragile vasculature, valve disease, inappropriate needle placement, or patient movement resulting in the infusing needle being pulled from the intended vessel or causing the needle to be pushed through the wall of the vessel. High injection pressures and/or rates of some modern procedures can increase the risk of extravasation. In computed tomography, for example, contrast injection flow rates can be in the range of 0.1 to 10 ml/s. Extravasation can cause serious injury to patients. In that regard, certain injection fluids such as contrast media or chemotherapy drugs can be toxic to tissue. It is, therefore, very important when performing fluid injections to detect extravasation as soon as possible and discontinue the injection upon detection.
Several extravasation detection techniques are known in the art. Two simple and very useful techniques for detecting extravasation are palpation of the patient in the vicinity of the injection site and simple visual observation of the vicinity of the injection site by a trained health care provider. In the palpation technique, the health care provider manually senses swelling of tissue near the injection site resulting from extravasation. By visual observation, it is also sometimes possible to observe directly any swelling of the skin in the vicinity of an injection site resulting from extravasation.
In addition to palpation and observation, there are a number of automated or sensor-base methods of detecting extravasation that may include automatic triggering of an alarm condition upon detection. Sensor configurations that also provide an area for palpation and/or observation are discussed, for example, in U.S. Pat. No. 6,408,204, assigned to the assignee of the present invention, the disclosure of which is incorporated herein by reference.
Several plethysmographic extravasation detection techniques and sensors are available. For example, mercury strain gauge plethysmographs measure the volume change resulting from venous blood flow in a cross sectional area of a limb of a patient. Air cuff or pulse volume recorder plethysmographs measure the changes in pressure within a recording cuff.
Impedance plethysmographs use low-frequency electromagnetic energy transmitted via galvanic contact with the skin to measure changes in the electrical impedance in a defined tissue volume of a limb. Detection of extravasation via impedance changes is disclosed, for example, in U.S. Pat. Nos. 5,964,703 and 5,947,910.
Photo-plethysmographs measure the optical scattering properties of capillary blood to detect the presence of extravasated fluids in tissue. An example of a photo-plethysmograph is described in U.S. Pat. No. 4,877,034.
A number of extravasation detection devices attempt to measure temperature differences to determine if an extravasation has occurred. For example, U.S. Pat. No. 4,647,281 discloses subcutaneous temperature sensing of extravasation to trigger an alarm. U.S. Pat. No. 5,954,668 also discloses use of a microwave antenna to sense temperature of tissue to detect extravasation.
In addition, U.S. Pat. No. 5,334,141 discloses a microwave extravasation detection system employing a reusable microwave antenna and a disposable attachment element for releasably securing the microwave antenna to a patient's skin over an injection site. The attachment element holds the antenna in intimate contact with the patient's skin to optimize microwave transfer therebetween. The sensor detect changes from normal microwave emissions from a patient that result from extravasation.
Published PCT International Application Nos. WO 03/009753 and WO 03/009752, assigned to the assignee of the present invention, the disclosures of which are incorporated herein by reference, disclose sensors that use electromagnetic energy such as microwave energy to sense changes in permittivity of tissue to sense buildup of fluids within the tissue to determine, for example, if extravasation or edema is present. The sensors include at least one electromagnetic energy transmitter for directing energy into a volume of tissue and at least one electromagnetic energy receiver to measure a resultant signal.
In many instances in which a medical device such as an extravasation sensor must be held in contact with a patient, adhesive tape is simply pulled over a device and adhered to the patient to maintain the device in connection with the patient. Likewise, many bandages or other tissue coverings include an adhesive material. Often it is difficult to remove such adhesive tapes, strips or sheets from connection with the patient. Moreover, removal of such adhesive materials from the patient is often a painful experience for the patient. U.S. patent application Ser. No. 11/082,209, entitled RELEASABLE APPLICATION SYSTEMS AND RELEASABLE MEDICAL DEVICE SYSTEMS, filed Mar. 16, 2005, assigned to the assignee of the present invention, the disclosure of which is incorporate herein by reference, discloses the use of releasable adhesive devices to attach various sensors to a patient and to provide a tissue covering after a sensor is removed.
Although some advances have been made in the attachment of medical devices, including sensors, to patients, a number of problems persist. For example, in a number of such devices such as the sensors disclosed in Published PCT International Application Nos. WO 03/009753 and WO 03/009752, a number of factors including, but not limited to, the nature of the contact (direct or indirect) of the sensor with the patient's tissue (for example, skin) and the position and/or orientation of the sensor(s) with respect to the patient and other medical devices can be important to the operation of the sensor. Moreover, many sensors and other medical devices have a number of operating components that are preferably attached to the patient or otherwise stabilized for proper operation and/or stabilization. Typically, attachment of such components requires the use of multiple strips of adhesive tape, which may not be readily available to medical personnel or may be cumbersome to obtain and apply. Moreover, such strips are typically not sterile and their use does not follow good aseptic technique.
It thus remains desirable to develop devices, systems and methods whereby a medical device can be releasably or removably attached to a patient.